1,319 research outputs found

    Comparison of ruminal lipid metabolism in dairy cows and goats fed diets supplemented with starch, plant oil or fish oil

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    16 páginas, 5 tablas, 1 figura.Direct comparison of cow and goat performanceand milk fatty acid responses to diets known to inducemilk fat depression (MFD) in the bovine revealsrelevant species-by-diet interactions in ruminal lipidmetabolism. Thus, this study was conducted to inferpotential mechanisms responsible for differences in therumen microbial biohydrogenation (BH) due to dietand ruminant species. To meet this objective, 12 cowsand 15 goats were fed a basal diet (control), a similardiet supplemented with 2.2% fish oil (FO), or a dietcontaining 5.3% sunflower oil and additional starch(+38%; SOS) according to a 3 × 3 Latin square designwith 25-d experimental periods. On the last day of eachperiod, fatty acid composition (by gas chromatography)and bacterial community (by terminal-RFLP),as well as fermentation characteristics, were measuredin rumen fluid samples. Results showed significant differencesin the response of cows and goats to dietarytreatments, although variations in some fermentationparameters (e.g., decreases in the acetate-to-propionateratio due to FO or SOS) were similar in both species.Main alterations in ruminal BH pathways potentiallyresponsible for MFD on the SOS diet (i.e., the shiftfrom trans-11 to trans-10 18:1 and related increases intrans-10,cis-12 18:2) tended to be more pronounced incows, which is consistent with an associated MFD onlyin this species. However, changes linked to FO-inducedMFD (e.g., decreases in 18:0 and increases in totaltrans-18:1) were stronger in caprine rumen fluid, whichmay explain their unexpected susceptibility (althoughless marked than in bovine) to the negative effect ofFO on milk fat content. Altogether, these results suggestthat distinct ruminal mechanisms lead to eachtype of diet-induced MFD and confirm a pronouncedinteraction with species. With regard to microbiota,differences between cows and goats in the compositionof the rumen bacterial community might be behindthe disparity in the microorganisms affected by theexperimental diets (e.g., Ruminococcaceae, Lachnospiraceae,and Succinivibrionaceae in the bovine, andPseudobutryrivibrio, Clostridium cluster IV, Prevotella,and Veillonellaceae in the caprine), which hinderedthe assignation of bacterial populations to particularBH steps or pathways. Furthermore, most relevantvariations in microbial groups corresponded to as yetuncultured bacteria and suggest that these microorganismsmay play a predominant role in the ruminal lipidmetabolism in both cows and goats.This study was supported by INRA (UMR1213; France) and the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2014-54587). P. G. Toral was granted a postdoctoral fellowship from Fundación Alfonso Martín Escudero (Madrid, Spain) and a research contract from the MINECO (Juan de la Cierva program).Peer reviewe

    Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

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    Prediction of bulk milk fatty acid composition based on farming practices collected through on-farm surveys

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    International audience; The aim of this study was to predict the fatty acid (FA) composition of bulk milk using data describing farming practices collected via on-farm surveys. The FA composition of 1,248 bulk cow milk samples and the related farming practices were collected from 20 experiments led in 10 different European countries at 44 degrees N to 60 degrees N latitude and sea level to 2,000 m altitude. Farming practice-based FA predictions [coefficient of determination (R-2) >0.50] were good for C16:0, C17:0, saturated FA, polyunsaturated FA, and odd-chain FA, and very good (R-2 >= 0.60) for trans-11 C18:1, trans-10 + trans-11 C18:1, cis-9,trans-11 conjugated linoleic acid, total trans FA, C18:3n-3, n-6:n-3 ratio, and branched-chain FA. Fatty acids were predicted by cow diet composition and by the altitude at which milk was produced, whereas animal-related factors (i.e., lactation stage, breed, milk yield, and proportion of primiparous cows in the herd) were not significant in any of the models. Proportion of fresh herbage in the cow diet was the main predictor, with the highest effect in almost all FA models. However, models built solely on conserved forage-derived samples gave good predictions for odd-chain FA, branched-chain FA, trans-10 C18:1 and C18:3n-3 (R-2 >= 0.46, 0.54, 0.52, and 0.70, respectively). These prediction models could offer farmers a valuable tool to help improve the nutritional quality of the milk they produce